- ID:
- ivo://CDS.VizieR/J/A+A/640/A78
- Title:
- Sunspot area catalogue revisited (1874-2019)
- Short Name:
- J/A+A/640/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long and consistent sunspot area records are important for understanding long-term solar activity and variability. Multiple observatories around the globe have regularly recorded sunspot areas, but such individual records only cover restricted periods of time. Furthermore, there are systematic differences between these records and require cross-calibration before they can reliably be used for further studies. We produce a cross-calibrated and homogeneous record of total daily sunspot areas, both projected and corrected, covering the period between 1874 and 2019. In addition, we generated a catalog of calibrated individual group areas for the same period. We compared the data from nine archives: Royal Greenwich Observatory (RGO), Kislovodsk, Pulkovo, Debrecen, Kodaikanal, Solar Optical Observing Network (SOON), Rome, Catania, and Yunnan Observatories, covering the period between 1874 and 2019. Cross-comparisons of the individual records were done to produce homogeneous and inter-calibrated records of daily projected and corrected areas. As in earlier studies, the basis of the composite is formed by the data from RGO. After 1976, the only datasets used are those from Kislovodsk, Pulkovo, and Debrecen observatories. This choice was made based on the temporal coverage and the quality of the data. While there are still 776 days missing in the final composite, these remaining gaps could not be filled with data from the other archives as the missing days lie either before 1922 or after 2016 and none of the additional archives cover these periods. In contrast to the SOON data used in previous area composites for the post-RGO period, the properties of the data from Kislovodsk and Pulkovo are very similar to those from the RGO series. They also directly overlap the RGO data in time, which makes their cross-calibration with RGO much more reliable. Indeed, comparing our area catalog with previous such composites, we find improvements both in data quality and coverage. We also computed the daily Photometric Sunspot Index, which is widely used, for example, in empirical reconstructions of solar irradiance.
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- ID:
- ivo://CDS.VizieR/J/A+A/584/A73
- Title:
- Sunspot areas and tilt angles
- Short Name:
- J/A+A/584/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims to estimate areas of sunspots observed by Schwabe in 1825-1867 and to calculate the tilt angles of sunspot groups. The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century.
143. Sunspot on 1921-2011
- ID:
- ivo://CDS.VizieR/J/A+A/601/A106
- Title:
- Sunspot on 1921-2011
- Short Name:
- J/A+A/601/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long-term sunspot observations are key to understanding and predicting the solar activities and its effects on space weather. Consistent observations, which are crucial for long-term variations studies, are generally not available due to upgradation/modification of observatories over the course of time. We present data for a period of 90 yr acquired from persistent observation at the Kodaikanal observatory in India. We aim to build a uniform sunspot area time series along with their positions for a 90-yr period between 1921 and 2011, as obtained from the newly digitized and calibrated white-light images from the Kodaikanal observatory. Our aim is to compare this new time series with known sources and confirm some of the earlier reported results with additional new aspects. We use an advanced semi-automated algorithm to detect the sunspots form each calibrated white-light image. Area, longitude and latitude of each of the detected sunspots are derived. Implementation of a semi-automated method is extremely necessary in such studies as it minimizes the human bias in the detection procedure. Daily, monthly, and yearly sunspot area variations, obtained from the Kodaikanal, compared well with the Greenwich sunspot area data. We find an exponentially decaying distribution for the individual sunspot area for each of the solar cycles. Analyzing the histograms of the latitudinal distribution of the detected sunspots, we find Gaussian distributions, in both the hemispheres, with centers at ~15{deg} latitude. The height of the Gaussian distributions are different for the two hemispheres for a particular cycle. Using our data, we show clear presence of Waldmeier effect, which correlates the rise time with the cycle amplitude. Using the wavelet analysis, we explored different periodicities on different time scales present in the sunspot area times series.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A46
- Title:
- Sunspot penumbra and umbral flashes models
- Short Name:
- J/A+A/627/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The solar chromosphere and the lower transition region are believed to play a crucial role in the heating of the solar corona. Models that describe the chromosphere (and the lower transition region), accounting for its highly dynamic and structured character are, so far, found to be lacking. This is partly due to the breakdown of complete frequency redistribution (CRD) in the chromospheric layers and also because of the difficulty in obtaining complete sets of observations that adequately constrain the solar atmosphere at all relevant heights. We aim to obtain semi-empirical model atmospheres that reproduce the features of the MgII H & K line profiles that sample the middle chromosphere with focus on a sunspot. We used spectropolarimetric observations of the CaII 8542{AA} spectra obtained with the Swedish 1-m Solar Telescope and used NICOLE inversions to obtain semi-empirical model atmospheres for different features in and around a sunspot. These were used to synthesize MgII H & K spectra using the RH1.5D code, which we compared with observations taken with the Interface Region Imaging Spectrograph (IRIS). Comparison of the synthetic profiles with IRIS observations reveals that there are several areas, especially in the penumbra of the sunspot, where most of the observed MgII H & K profiles are very well reproduced. In addition, we find that supersonic hot downflows, present in our collection of models in the umbra, lead to synthetic profiles that agree well with the IRIS MgII H & K profiles, with the exception of the line core. We put forward and make available four semi-empirical model atmospheres. Two for the penumbra, reflecting the range of temperatures obtained for the chromosphere, one for umbral flashes, and a model representative of the quiet surroundings of a sunspot. These are available in electronic as well as in table formats.
- ID:
- ivo://CDS.VizieR/VI/138
- Title:
- Sunspots catalogues, 1853-1870
- Short Name:
- VI/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the 19th century, several astronomers observed sunspots obtaining their positions and, occasionaly, their areas. These observations were published in large tables that have remained in the anonymity until now. The observations made by Richard C. Carrington, Christian H. F. Peters and Warren de la Rue (and their respective collaborators) were published in different articles. The total number of positions evaluated by these three observers was of 26,641 (Carrington: 4,900; Peters: 14,040; and de la Rue: 7,701). In this work, we transformed more of 400 pages of numerical tables to a machine readable format. Moreover, we carried out a cursory analysis to detect possible mistakes in the reading or in the original transcription.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A21
- Title:
- Sun UV spectrum (06/06/2008-26/04/2009)
- Short Name:
- J/A+A/600/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SOLar SPECtrum (SOLSPEC) experiment is part of the Solar Monitoring Observatory (SOLAR) payload, and has been externally mounted on the Columbus module of the International Space Station (ISS) since 2008. SOLAR/SOLSPEC combines three absolutely calibrated double monochromators with concave gratings for measuring the solar spectral irradiance (SSI) from 166nm to 3088nm. This physical quantity is a key input for studies of climatology, planetary atmospheres, and solar physics. A general description of the instrument is given, including in-flight operations and performance of the ultraviolet (UV) channel from 175nm to 340nm. We developed a range of processing and correction methods, which are described in detail. For example, methods for correcting thermal behavior effects, instrument linearity, and especially the accuracy of the wavelength and absolute radiometric scales have been validated by modeling the standard uncertainties. The deliverable is a quiet Sun UV reference solar spectrum as measured by SOLAR/SOLSPEC during the minimum of solar activity prior to cycle 24. Comparisons with other instruments measuring SSI are also presented.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A108
- Title:
- Sun velocities from GOLF instrument
- Short Name:
- J/A+A/617/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent claims of g-mode detection have restarted the search for these potentially extremely important modes. These claims can be reassessed in view of the different data sets available from the SoHO instruments and ground-based instruments. We produce a new calibration of the GOLF data with a more consistent p-mode amplitude and a more consistent time shift correction compared to the time series used in the past. The calibration of 22 years of GOLF data is done with a simpler approach that uses only the predictive radial velocity of the SoHO spacecraft as a reference. Using p modes, we measure and correct the time shift between ground- and space-based instruments and the GOLF instrument. The p-mode velocity calibration is now consistent to within a few percent with other instruments. The remaining time shifts are within +/-5s for 99.8% of the time series.
- ID:
- ivo://CDS.VizieR/J/A+A/528/A113
- Title:
- Synthetic lines in the Sun
- Short Name:
- J/A+A/528/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have computed synthetic spectra from a realistic 3D numerical simulation of the solar photosphere. We provide the spatially averaged spectra for selected lines that are commonly used on solar applications. These data can be used to calibrate Doppler velocity measurements in the solar photosphere. The calculations are carried out along the solar disk from heliocentric angle mu=1.0 to mu=0.3.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A113
- Title:
- The solar CNO abundances
- Short Name:
- J/A+A/656/A113
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Carbon, nitrogen, and oxygen are the fourth, sixth, and third most abundant elements in the Sun. Their abundances remain hotly debated due to the so-called solar modelling problem that has persisted for almost 20 years. We revisit this issue by presenting a homogeneous analysis of 408 molecular lines across 12 diagnostic groups, observed in the solar intensity spectrum. Using a realistic 3D radiative-hydrodynamic model solar photosphere and local thermodynamic equilibrium (LTE) line formation, we find log{epsilon}C=8.47+/-0.02, log{epsilon}N=7.89+/-0.04, and log{epsilon}O=8.70+/-0.04. The stipulated uncertainties mainly reflect the sensitivity of the results to the model atmosphere; this sensitivity is correlated between the different diagnostic groups, which all agree with the mean result to within 0.03dex. For carbon and oxygen, the molecular results are in excellent agreement with our 3D non-LTE analyses of atomic lines. For nitrogen, however, the molecular indicators give a 0.12dex larger abundance than the atomic indicators, and our best estimate of the solar nitrogen abundance is given by the mean: 7.83dex. The solar oxygen abundance advocated here is close to our earlier determination of 8.69dex, and so the present results do not significantly alleviate the solar modelling problem.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/115
- Title:
- The solar flare complex network
- Short Name:
- J/ApJ/847/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the characteristics of the solar flare complex network. The limited predictability, nonlinearity, and self-organized criticality of the flares allow us to study systems of flares in the field of the complex systems. Both the occurrence time and the location of flares detected from 2006 January 1 to 2016 July 21 are used to design the growing flares network. The solar surface is divided into cells with equal areas. The cells, which include flares, are considered nodes of the network. The related links are equivalent to sympathetic flaring. The extracted features demonstrate that the network of flares follows quantitative measures of complexity. The power-law nature of the connectivity distribution with a degree exponent greater than three reveals that flares form a scale-free and small-world network. A large value for the clustering coefficient, a small characteristic path length, and a slow change of the diameter are all characteristics of the flares network. We show that the degree correlation of the flares network has the characteristics of a disassortative network. About 11% of the large energetic flares (M and X types in GOES classification) that occurred in the network hubs cover 3% of the solar surface.
